The challenge to meet the ever-increasing demand for oil includes increasing crude oil recovery from heavy oil reservoirs. This challenge has resulted in expanding efforts to develop alternative cost efficient oil recovery processes (Kianipey, S. A. and Donaldson, E. C. 61st Annual Technical Conference and Exhibition, New Orleans, La., USA, Oct. 5-8, 1986). Heavy hydrocarbons in the form of petroleum deposits and oil reservoirs are distributed worldwide. These oil reservoirs are measured in the hundreds of billions of recoverable barrels. Because heavy crude oil has a relatively high viscosity, it is essentially immobile and cannot be easily recovered by conventional primary and secondary means. Thus there is a need for various methods to enhance bioremediation and oil recovery.
Microbial Enhanced Oil Recovery (MEOR) is a methodology for increasing oil recovery by the action of microorganisms (Brown, L. R., Vadie, A. A., Stephen, O. J. SPE 59306, SPE/DOE Improved Oil Recovery Symposium, Oklahoma, Apr. 3-5, 2000). MEOR research and development is an ongoing effort directed at discovering techniques to use microorganisms to modify crude oil properties to benefit oil recovery (Sunde E., Beeder, J., Nilsen, R. K. Torsvik, T., SPE 24204, SPE/DOE 8th Symposium on enhanced Oil Recovery, aerobic or anaerobic conditions (Mechichi Tahar et. al., Arch Microbiol., (2002), 178: 26-35 Tulsa, Okla., USA, Apr. 22-24, 1992). Thus, identifying microorganisms that could be used to enhance oil recovery under economic conditions, can grow on oil under anaerobic conditions without the need for nutrient supplementation or long term enrichment of indigenous microorganisms which can be used, in a cost-efficient way, to improve bioremediation is of significant importance.
Particular strains of denitrifying bacteria belonging to the Beta-Proteobacteria related genera, e.g., Azoarcus and Thauera have been shown to grow on oil and or oil constituents under anaerobic conditions without the need for nutrient supplementation (Anders et. al. Int. J. Syst. Evol. Microbiol., (1995), 45: 327-333). The anaerobic pathways involved in hydrocarbon metabolism have been studied in Thauera and Azoarcus species. An important class of enzymes in these pathways are benzylsuccinate synthases (bss), which catalyze the metabolism of simple aromatic compounds and are synthesized by the bss operon. These enzymes have been identified in Thauera and Azoarcus species and shown to possess varied substrate specificities. For example, while the bss enzyme of an Azoarcus strain converts toluene, all xylene and cresol isomers to the corresponding succinate adducts, the same enzyme from Thauera aromatica is active with toluene and all cresols, but not with any xylene isomers. Thus, differences in substrate specificity of the bss enzymes in these two denitrifying bacterial strains contributes to their varied ability in utilization of different aromatic hydrocarbons (Verfürth et al., Arch Microbiol., (2004), 181: 155-162). An additional pathway of anaerobic hydrocarbon catabolism has been reported in selected Azoarcus strains (i.e. strains EB1, and EbN1) but has not been identified in any Thauera strains to date. In this pathway, ethylbenzene and n-propylbenzene are oxidized under anaerobic conditions by the ethylbenzene dehydrogenase (ebd) enzyme (Boll, et al., Curr. Op. Chem. Biol., (2002), 6: 604-611)
Ultimately, most of the aromatic compounds are converted to the central intermediate benzoyl-CoA via different metabolic pathways, where they undergo enzymatic benzene ring cleavage via Benzoyl-CoA reductase (bcr) (Mechichi, et al., Arch. Microbiol. (2002), 178: 26-35). While similar enzymes are widely distributed among denitrifying bacteria much of the information reported to date is derived from a bcr enzyme isolated from Thauera aromatica. 
This disclosure relates to a novel Thauera strain AL9:8, defined by its ability to grow on crude oil, and by the presence of a gene sequence derived from the ebdA-like gene hitherto unidentified in Thauera species. Thus the present disclosure, relates to both the identification and use of a microorganism that grows in the presence of crude oil, and modifies its physico-chemical properties to enhance bioremediation under denitrifying conditions.